Get dotCover path - teamcity.dotcover.home

How can my Powershell build script read the path to TeamCity's bundled dotCover.exe?

The build parameters list show this path value under "Actual Parameters on Agent - Configuration Parameters" in this build parameter: "teamcity.dotcover.home"

These statements work to read environment variable values:
write-host "TEAMCITY_PROJECT_NAME: $env:TEAMCITY_PROJECT_NAME"
write-host "TEAMCITY_BUILDCONF_NAME: $env:TEAMCITY_BUILDCONF_NAME"

These statements DO NOT work:
write-host "TEAMCITY_DOTCOVER_HOME: $env:TEAMCITY_DOTCOVER_HOME"
write-host "TEAMCITY_DOTCOVER_HOME: $system:TEAMCITY_DOTCOVER_HOME"
write-host "TEAMCITY_DOTCOVER_HOME: $TEAMCITY_DOTCOVER_HOME"

How can my script read this value?